Either way, once you have the endorsement on one of them, you can fly the other.
. Yes, that's what the class endorsement says.
However, getting a Baron endorsement is one thing and reasonably easy. Convincing someone to hire you a Baron after you have gained the endorsement is something else again.
Most organisations hiring out Barons will insist on a minimum of MECIR, 500 PIC hours total twin time with at least 100 PIC type hours on the Be55/58 (time on the Be95 Travelair will not count as contributing towards the 100 Be55/58 type hours).
So the serious question you need to ask yourself is why spend the money on a Baron endorsement when you most likely won't be able to hire one after you have gained your endorsement anyway? However, if you know someone who is prepared to hire one out to you privately, go for it. The alternative is to build up Be55/58 PIC type hours with another experienced Baron pilot in the other seat (provided the insurance company agrees) until such time as you meet the minimum hiring requirements.